We've just finished up the first paper resulting from our observations of the Kepler field with the GBT. Preprint available at http://seti.berkeley.edu/sites/default/files/kepler_seti_I_siemion_et_al_preprint.pdf

Re: sensitivity, we have to work with what we have! However, distributing these data to SETI@Home volunteers (coming soon!) will improve our sensitivity by a factor of between ~few - 10, depending on how the work units are structured. Arecibo is about as bright as Earth transmitters get, and it's just out of reach for most of the systems we targeted. For more nearby systems, an exo-Arecibo would be readily detectable. In this experiment, the largest contributor to the total noise in the observing system was the radio receiver noise.

Re: intentional signals, you're correct that the most plausible signal we might expect to receive in an experiment like this is an intentional beacon. It is indeed difficult to imagine that a very advanced civilization would 'leak' huge amounts of energy in the form of narrow band radio signals inadvertently. However, we have to be careful not to over think this too much. Remember, the principal reasons why we search for narrow-band signals are 1. they are obvious indicators of technology and 2. they transit the interstellar medium very readily. These two facts are true regardless of the motivations of the transmitting civilization.

Thanks, found it also on: http://arxiv.org/pdf/1302.0845.pdf :)
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